Skip to Main Content

++

PHENOBARBITAL

++

Phenobarbital is a barbituric acid derivative with hypnotic activity and central nervous system (CNS) depressant effects. Phenobarbital is one of the oldest anticonvulsant agents still used in clinical practice. It is FDA-approved for short-term sedation/hypnosis and treatment of generalized or partial onset seizures and provides an alternative to treat refractory status epilepticus. It is less commonly used as the first-line anticonvulsant due to disadvantages such as cognitive impairment, respiratory depression, sedation, and significant drug interactions. The anticonvulsant activity of phenobarbital is thought to be due to its effect on postsynaptic GABA receptors, which increases seizure threshold but the full mechanism is not completely understood.1 Phenobarbital has also been used off-label to treat alcohol withdrawal, neonatal seizures, febrile seizures, neonate hyperbilirubinemia, and adults with congenital nonhemolytic unconjugated hyperbilirubinemia or chronic cholestasis.

++

DOSING

++

Phenobarbital is available in an injectable formulation, which can be given intravenously or intramuscularly, and oral formulation (tablets and solution) (see Table 14-1). In adult patients, the recommended dose for sedation and hypnosis is 30–100 mg/day and titrated upward slowly to 400 mg/day. For epilepsy management, dosing is usually weight-based where an adult maintenance dose of 2 mg/kg/day would result in a predicted steady-state concentration of 20 mg/L. A case report suggests that dosing should be with total body weight.2 If immediate therapeutic concentrations are required a loading dose of 15–20 mg/kg can be administered intravenously or orally in three divided doses every 2 to 3 hours. When phenobar-bital is administered intravenously, a rate of no more than 50 mg/min is recommended to avoid toxicity with the propylene glycol diluent.3 Maintenance dosing in children (1–15 years old) is usually 3–5 mg/kg/day and for neonates (<2 weeks of age) is 2–4 mg/kg/day.4 Because phenobarbital has a long half-life, it can be dosed once daily; however, initially excessive sedation may limit the ability to use once-daily dosing. Excessive sedation can be minimized by gradually increasing the dose using the following schedule: Start with 25 percent of the final daily dose each evening for 5-–7 days and if tolerated the dose can then be increased to 50 percent of the final recommended dose for the next 5–7 days and then 75 percent of the final recommended dose for the next 5–7 days. The titration to the final dose should be completed by the fourth week of therapy. Steady-state serum concentrations should be checked about 3–4 weeks after achieving the total maintenance dose. A serum phenobarbital concentration targeting between 10–40 mg/L is considered within optimum range for therapeutic drug monitoring (TDM).5

++
Table Graphic Jump Location
TABLE 14-1Dosage Formulations and Strengths

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.

Ok

About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessPharmacy Full Site: One-Year Subscription

Connect to the full suite of AccessPharmacy content and resources including 30+ textbooks such as Pharmacotherapy: A Pathophysiologic Approach and Goodman & Gilman's The Pharmacological Basis of Therapeutics, high-quality videos, images, and animations, interactive board review, drug and herb/supplements databases, and more.

$595 USD
Buy Now

Pay Per View: Timed Access to all of AccessPharmacy

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.